Articulating, self-centering truck for personal mobility vehicles

ABSTRACT

One variation of a system includes: a cam block mounted to a deck of a scooter and defining cam lobes arranged about a pivot feature and cam heels between the set of cam lobes; a pivot block pivotably coupled to the pivot feature and defining followers riding over the cam lobes; a pair of wheel uprights locating a pair of wheel assemblies; a first lateral link extending between and coupled to the pair of wheel uprights and pivotably coupled to the pivot block; a second lateral link extending between and coupled to the pair of wheel uprights, vertically offset from the first lateral link, and coupled to the pivot block between pair of wheel uprights; and a spring element driving the followers of the pivot block into cam heels to bias the second lateral link toward a neutral position.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 63/034,764, filed on 4 Jun. 2020, which is hereby incorporated inits entirety by this reference.

This application is a continuation-in-part application of U.S. patentapplication Ser. No. 17/236,973, filed on 21 Apr. 2021, which is acontinuation application of U.S. patent application Ser. No. 16/535,004,filed on 7 Aug. 2019, which claims the benefit of U.S. ProvisionalApplication No. 62/715,738, filed on 7 Aug. 2018, each of which isincorporated in its entirety by this reference.

TECHNICAL FIELD

This invention relates generally to the field of personal mobility andmore specifically to a new and useful articulating, self-centering truckfor a personal mobility vehicle in the field of personal mobility.

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1A and 1B are schematic representations of a truck;

FIGS. 2A and 2B are schematic representations one variation of thetruck;

FIG. 3 is a schematic representation of one variation of the truck;

FIG. 4 is a flowchart representation of one variation of the truck and apersonal mobility vehicle;

FIG. 5 is a schematic representation of one variation of the truck;

FIG. 6 is a schematic representation of one variation of the truck;

FIG. 7 is a flowchart representation of one variation of the truck;

FIG. 8 is a schematic representation of one variation of the truck;

FIG. 9 is a flowchart representation of one variation of the truck; and

FIG. 10 is a flowchart representation of one variation of the truck; and

FIG. 11 is a flowchart representation of one variation of the truck; and

FIGS. 12A, 12B and 12C are schematic representations one variation ofthe personal mobility vehicle;

FIG. 13 is a flowchart representation of one variation of the personalmobility vehicle; and

FIG. 14 is a flowchart representation of one variation of the personalmobility vehicle.

DESCRIPTION OF THE EMBODIMENTS

The following description of embodiments of the invention is notintended to limit the invention to these embodiments but rather toenable a person skilled in the art to make and use this invention.Variations, configurations, implementations, example implementations,and examples described herein are optional and are not exclusive to thevariations, configurations, implementations, example implementations,and examples they describe. The invention described herein can includeany and all permutations of these variations, configurations,implementations, example implementations, and examples.

1. Truck

As shown in FIGS. 1A, 1B, 2A, and 2B, a truck 100 of a personal mobilityvehicle 200 (e.g., a human-powered or motorized scooter, a skateboard)includes: a cam block 110; a pivot block 120; a right wheel upright 130;a right wheel axle 133 extending outwardly from the right wheel upright130 and configured to locate a right wheel assembly 132; a left wheelupright 140; a left wheel axle 143 extending outwardly from the leftwheel upright 140 and configured to locate a left wheel assembly 142; anupper lateral link 150 coupled to the right wheel upright 130 and theleft wheel upright 140 and coupled to and pivoting about the upper pivotbore 111; a lower lateral link 151 coupled to the right wheel upright130, the left wheel upright 140 below the upper lateral link 150, andthe pivot block 120 between the right wheel upright 130 and the leftwheel upright 140; and a spring element 180. The cam block 110 isconfigured to mount to a deck 212 of a personal mobility vehicle 200 anddefines: an upper pivot bore 111; a lower pivot bore 112 located belowthe upper pivot bore 111; and a set of cam lobes 114 arranged about thelower pivot bore 112. The pivot block 120: is coupled to and pivotsabout the lower pivot bore 112; and defines a set of followers 122configured to ride over the set of cam lobes 114. The spring element 180is coupled to the pivot block 120 and is configured to drive the set offollowers 122 of the pivot block 120 against the set of cam lobes 114 ofthe cam block 110 to bias the lower lateral link 151 toward a neutralposition.

One variation of the system includes a cam block 110: configured tomount to a deck 212 of a scooter and defining: a first pivot feature(e.g., a bore, a counterbore 113, a threaded shaft); a second pivotfeature vertically offset from the first pivot feature; a set of camlobes 114 arranged about the second pivot feature; and a set of camheels 115 between the set of cam lobes 114. This variation of the systemalso includes a pivot block 120: coupled to and pivoting about thesecond pivot feature; and defining a set of followers 122 configured toride over the set of cam lobes 114. This variation of the system furtherincludes: a pair of wheel uprights configured to locate a pair of wheelassemblies; a first lateral link extending between and coupled to thepair of wheel uprights and coupled to and pivoting about the first pivotfeature; and a second lateral link extending between and coupled to thepair of wheel uprights, vertically offset from the first lateral link,and coupled to the pivot block 120 between the pair of wheel uprights.In this variation, the system also includes a spring element 180 coupledto the pivot block 120 and configured to drive the set of followers 122of the pivot block 120 into the set of cam heels 115 to bias the secondlateral link toward a neutral position.

A similar variation of the system includes: a deck 212 configured tosupport a user; a cam block 110 mounted to the deck 212 and defining afirst pivot feature, a second pivot feature vertically offset from thefirst pivot feature, and a first set of lobes arranged about the secondpivot feature; a pivot block 120 coupled to and pivoting about the lowerpivot feature and defining a second set of lobes configured to ride overthe first set of lobes; a right wheel upright 130; a left wheel upright140; a right wheel assembly 132 mounted to the right wheel upright 130;a left wheel assembly 142 mounted to the left wheel upright 140; and afirst lateral link pivotably coupled to the first pivot feature. Thisvariation of the system also includes: a second lateral link coupled tothe pivot block 120 and cooperating with the right wheel upright 130,the left wheel upright 140, and the first lateral link to form afour-bar linkage that locates the right wheel assembly 132 and the leftwheel assembly 142 on the cam block 110. This variation of the systemfurther includes a spring element 180 coupled to the pivot block 120 andconfigured to drive the set of followers 122 in the pivot block 120against the set of cam lobes 114 of the cam block 110 to bias the lowerlateral link 151 toward a neutral position, the cam block 110 and thepivot block 120 cooperating to locate a top of the deck 212 parallel tothe second lateral link in the neutral position.

2. Scooter

The truck 100 is described herein as installed (e.g., at time ofmanufacture or retrofit) at the rear of a manually-powered or motorizedthree-wheeled scooter to form a “rear truck.” As shown in FIGS. 12A,12B, and 12C, the scooter can include: a deck 212 configured to supporta rider; the truck 100 supporting a pair of rear wheel assemblies andmounted to the rear of the deck 212; a stem 224 mounted to the front ofthe deck 212 and coupled to a front wheel assembly 202 (e.g., a hubmotor, wheel, and tire assembly); a handlebar 226 connected to the stepopposite the front wheel assembly 202; a throttle assembly coupled tothe handlebar 226; a battery (e.g., arranged in the deck 212) configuredto supply electrical energy to the front wheel assembly 202 responsiveto actuation of the throttle assembly.

In one variation shown in FIG. 13, the deck 212 is segmented into afront deck section 210 and a rear deck section 213 that are configuredto fold (or “collapse”) about a deck hinge 214 in order to enable arider to transition the scooter between “go,” “tow,” and “stow” modes(i.e., operable, lugging, and storage states). In this variation, thedeck 212 includes: a front deck section 210 supporting the stem 224 andfront wheel assembly 202; a rear deck section 213 supporting the reartruck 100 opposite the front deck section 210; a deck hinge 214interposed between the front deck section 210 and the rear deck section213; and a deck latch configured to selectively lock the deck hinge 214in the closed deck position. In this variation, the deck hinge 214 canbe operable in: an open deck position to locate the front deck section210 tangent to the rear deck section 213 to form a substantiallycontinuous and substantially planar deck surface and to locate thescooter in a long-wheelbase configuration; and in a closed deck positionto separate the front deck section 210 from the rear deck section 213,to locate the scooter in a short-wheelbase configuration, and to locatethe deck hinge 214 above the front and rear wheel assemblies.

2. Applications

Generally, the system defines a truck 100 for a personal mobilityvehicle 200 and includes: a spring element 180; a cam block 110 affixedto a deck 212 of the personal mobility vehicle 200 and defining amulti-lobed cam pivot block 120 pivotably coupled to the cam block 110and sprung against the set of cam lobes 114 of the cam block 110 by thespring element 180; and a four-bar linkage—including a pair of wheeluprights connected by a pair of (parallel) lateral links—that locates apair of wheel axles and a pair of rear wheel assemblies. A first laterallink in this pair is pivotably coupled to the cam block 110, and asecond (e.g., lower) lateral link is mounted to the pivot block 120. Thespring element 180 drives a set of followers 122 arranged on the distalend of the pivot block 120 into the set of cam lobes 114 of the camblock 110 to bias the second lateral link toward a neutral position inwhich the second lateral link is approximately parallel to a surface ofthe deck 212.

For example, the personal mobility vehicle 200 can include a three- orfour-wheeled manually-powered or electric scooter or skateboard. The camblock 110 defines: an upper pivot bore 111; a lower pivot bore 112; acounterbore 113 arranged about the lower pivot bore 112; and a tri-lobedcam including a set of three cam lobes 114 separated by a set of threecam heels 115 arranged in the base of the counterbore 113 anddistributed radially about the lower pivot bore 112. The pivot block120: can include a boss arranged in the counterbore 113; can include aset of followers 122 arranged on the distal end of the boss and driveninto the cam heels 115 in the base of the counterbore 113 by the springelement 180; and can be pivotably coupled to the lower pivot bore 112 bya lower longitudinal shaft 161. A lower lateral link 151 can be fastenedto or physically coextensive (e.g., defining a unitary structure with)the pivot block 120. An upper longitudinal shaft 160 can pivotablycouple the upper lateral link 150 to the cam block no. The springelement 180: can include a coil spring arranged between the cam block noand an end of the lower longitudinal shaft 161 opposite the pivot block120; and can draw the boss of the pivot block 120 into the counterbore113 to maintain engagement between the followers 122 and the cam lobes114, drive the followers 122 in to the cam heels 115, bias the lowerlateral link 151 toward the neutral position, and thus bias the scootertoward an upright position in which the surface of the deck 212 isapproximately parallel with an adjacent ground surface.

Thus, with the truck 100 is mounted to the deck 212 of the scooter, thefollowers 122 on the end of the pivot block 120 can ride up the camlobes 114 in the cam block 110 as the deck 212 of the scooter rolls (or“pivots”) about its roll axis, such as when a rider leans (or “carves”)the scooter around a turn. As the followers 122 ride up the cam lobes114, the cam lobes 114 can drive the pivot block 120 out of the camblock 110, thereby compressing the spring element 180, increasing aspring force applied by the spring element 180 between the cam block 110and the pivot block 120, and increasing a restoring force on the pivotblock 120 to drive the followers 122 back toward the cam heels 115 andthus return the deck 212 to the neutral (e.g., horizontal) position.Therefore, the pivot block 120, the cam block 110, and the spring cancooperate to automatically bias the truck 100 to the neutral position,thereby: maintaining a high degree of stability of the deck 212 evenwhen stopped; and enabling a rider to more easily mount the scooter,balance on the deck 212, maneuver the scooter at low speed, and dismountthe scooter once stopped.

More specifically, the pivot block 120, the cam block 110, and thespring element 180 can cooperate to: self-center and stabilize thefour-bar linkage—defined by the upper and lower lateral links and theleft and the right wheel uprights—back to a neutral position followingchanges in weight distribution on the deck 212 (e.g., when the ridersteps onto or off of the deck 212 or when the rider rotation leansthrough a turn, each of which may tilt or rotate the deck 212 and applya torque to the cam block 110); exhibit increasing resistance to roll atgreater roll angles of the deck 212; prevent excess roll of the deck212; and enable the rear wheel assemblies to maintain ground contact(and steer) over a wide range of lean angles, thereby yielding greaterstability, comfort, and control for the rider throughout a range ofoperational speeds and maneuvers.

3.1 Example

In one example shown in FIG. 3, the cam block 110 includes: an upperpivot bore 111; a lower pivot bore 112 offset below the upper pivot bore111; and a set of (e.g., three) hemi-spherical receptacles radiallyoffset by 120° about the lower pivot bore 112 and configured to accept acomplementary set of hardened steel spherical bearings that cooperate toform the set of cam lobes 114. In this example, the upper lateral link150 is mounted to the cam block 110 via an upper longitudinal shaft 160that runs through the upper pivot bore 111. The pivot block 120: ismounted to the lower lateral link 151; defines a set of threecomplementary followers 122 opposite the lower lateral link 151 andconfigured to run against the cam lobes 114 formed by the set ofspherical bearings in the cam block 110; and is pivotably coupled to thecam block 110 via a lower longitudinal shaft 161 that runs through thelower pivot bore 112. The spring element 180: is arranged between aretainer 163 (e.g., a threaded nut) on a distal end of the lowerlongitudinal shaft 161—opposite the pivot block 120—and the cam block110; and is configured to pull (or “tension,” “draw”) the followers 122of the pivot block 120 into the cam lobes 114 in the cam block 110.

The spring element 180 thus exerts a linear force—parallel to alongitudinal axis of the cam block 110 and/or parallel to the sagittalplane of the deck 212—on the pivot block 120 to drive the followers 122of the pivot block 120 into cam heels 115 between the cam lobes 114 andto thus retain the truck 100 in a neutral position. When a change inweight distribution on the deck 212 causes the deck 212 to pivot aboutits roll axis relative to the ground during operation, the cam block 110similarly rolls relative to the ground, thereby: pivoting the cam lobes114 relative the followers 122 on the pivot block 120, which is locatedin a (nearly) fixed roll orientation by the four-bar linkage and thewheel assemblies; driving the followers 122 off of the cam heels 115 andup the cam lobes 114; driving the pivot block 120 out of (e.g.,rearward) the cam block 110; and (further) compressing the springelement 180 between the cam block 110 and the retainer 163. When(further) compressed, the spring element 180 exerts an increasing linearforce—parallel to the longitudinal axis of the cam block 110 and/orparallel to the sagittal plane of the deck 212—to force the followers122 of the pivot block 120 back down the cam lobes 114.

Furthermore, contact between the followers 122 in the pivot block 120and the cam lobes 114 in the cam block 110 can transform this linearforce applied by the spring element 180 into a torque (or a “restoringforce”) on the lower lateral link 151 opposite and proportional to theroll angle of the deck 212, thereby stabilizing the deck 212, preventingexcess roll of the deck 212 during operation, and automatically biasingthe deck 212 back to the neutral position.

Furthermore, in the foregoing example, the spherical bearings in the camblock 110 can rotate within their hemi-spherical receptacles and canroll along followers 122 of the pivot block 120 as the deck 212 tiltsabout its roll axis, thereby reducing friction and wear along the camlobes 114 and the followers 122.

In this example, and as shown in FIGS. 1A and 2A, the left and rightwheel axles 143, 133 can extend outwardly from the left and right wheeluprights 140, 130, respectively, above a lateral centerline between theupper and lower lateral links 150, 151, thereby setting the roll centerof the truck 100 below the wheel axles and improving the stability ofthe scooter throughout a range of operational speeds.

3.2 Adjustment

Additionally, the truck 100 can enable a rider to customize therestoring force applied by the truck 100 to the personal mobilityvehicle 200 (hereinafter the “scooter”)—such as per degree of roll ofthe deck 212—and therefore customize stability of the deck 212. Forexample, the rider or a technician may exchange a weaker spring element(e.g., a first coil spring or elastomeric bushing exhibiting a firstspring constant) for a stiffer spring element 180 (e.g., a second coilspring or elastomeric bushing exhibiting a second spring constantgreater than the first spring constant) in order to increase therestoring force applied by the truck 100 per degree of roll of the deck212 and thus increase stability of the scooter both when stopped andwhen in motion. Conversely, the rider or a technician may exchange thestiffer spring element 180 for the weaker spring element 180 in order todecrease this restoring force applied by the truck 100 per degree ofroll of the deck 212 and thus enable more rapid carving (or “slalom”)motions with the scooter in motion.

Additionally or alternatively, the scooter can include a mechanical orelectromechanical dynamic stability control configured to adjust preloadof the spring element 180 during operation of the scooter. For example,the truck 100 can include a nut threaded onto the lower longitudinalshaft 161 between the spring element 180 and the leading end of thelower longitudinal shaft 161. In this example, a foot-operatedpedal—mounted near a rear of the deck 212—can include a bimodal ratchetcoupled to the nut via a set of cables. Manual operation of the footpedal in a first ratchet mode (e.g., in a first direction) can thustighten the nut on the lower longitudinal axle, compress the springelement 180, increase preload of the spring element 180, and thusincrease the restoring force applied by the truck 100 on the deck 212over the full range of roll angles of the scooter. Conversely, manualoperation of the foot pedal in a second ratchet mode (e.g., in a seconddirection) can loosen the nut on the lower longitudinal axle, releasethe spring element 180, decrease preload of the spring element 180, andthus decrease the restoring force applied by the truck 100 on the deck212 over the full range of roll angles of the scooter.

In a similar example, the scooter can include a hand-actuated levermounted on its handlebars 226 and similarly coupled to the nut such thatmanual operation of the hand-actuated lever by the rider adjusts the nuton the lower longitudinal axles and thus adjusts preload of the springelement 180.

In a similar implementation, the system includes a gearhead motorcoupled to the nut—such as via toothed gears or a timing belt—and canrotate the nut on the lower longitudinal shaft 161 to selectivelytighten and loosen the nut on the lower longitudinal axles and thusadjust preload of the spring element 180, such as: responsive to manualinput at an electronic button or other control interface on thehandlebars 226 of the scooter; or responsive to a control output of astability control module 170 in the scooter (e.g., as a function ofspeed of the scooter). For example, the stability control module 170can: monitor the speed of the scooter based on a wheel speed of thefront wheel assembly 202 of the scooter; automatically actuate thegearhead motor in a first direction to tighten the nut, increase preloadof the spring element 180, and thus increase stability of the scooter atlow speeds (e.g., below 3 miles per hour) and at high speeds (e.g.,above 15 miles per hour); and automatically actuate the gearhead motorin a second direction to loosen the nut, decrease preload of the springelement 180, and thus to increase mobility of the scooter at moderatespeeds (e.g., between 3 miles per hour and 15 miles per hour).

3.3 Other Vehicles

While the truck 100 is described herein as a rear truck 100 for amotorized, three-wheeled scooter with a folding (e.g., collapsible) deck212 as described above, the truck 100 can be additionally oralternatively mounted to: the front or rear of a motorized scooter witha fixed deck 212; a manual (e.g., non-motorized) scooter; a longboard; ashort skateboard; a street luge; a seated scooter; or a personalmobility vehicle 200 of any other type. The truck 100 can thus define afront or rear truck 100 configured to improve roll stability of thevehicle and thus increase rider comfort over a range of operating speedsof the vehicle. Additionally and/or alternatively, components of thetruck 100 can be resized and mounted to a longboard, a short skateboard,a street luge, a seated scooter, or other personal mobility vehicle 200to improve stability (and/or enable adjustable stability controls) ofthe vehicle and increase rider comfort during operation.

4. Four-Bar Linkage and Wheel Axles

As shown in FIGS. 1B and 2B, the truck 100 includes a four-bar linkagepivotably coupled to the cam block 110 and configured to locate a pairof wheel axles and a pair of wheel assemblies. In particular, thefour-bar linkage includes: an upper lateral link 150 pivotably coupledto the cam block 110 via an upper longitudinal shaft 160; a lowerlateral link 151 mounted to (e.g., rigidly coupled to) the pivot block120, which is pivotably coupled to the cam block 110 via a lowerlongitudinal shaft 161; a right wheel upright 130 pivotably coupled (or“pinned”) to the right ends of the upper and lower lateral links 150,151 and supporting a right wheel assembly 132; and a left wheel upright140 pivotably coupled to the left ends of the upper and lower laterallinks 150, 151 and supporting a left wheel assembly 142.

In one implementation, the upper lateral link 150 and the lower laterallink 151 include aluminum (6061 aluminum, 7075 aluminum) or steel (e.g.,303 stainless steel) struts of similar or identical widths. For example,the upper and lower lateral links 150, 151 can be forged and/or machinedfrom billet.

The left and right wheel uprights 140, 130 can be machined, cast,forged, or molded, etc. in aluminum, steel, or a fiber-reinforcedcomposite, etc. In one example shown in FIGS. 1A and 2A, the left andright wheel uprights 140, 130 are configured to fasten to the ends ofthe upper and lower lateral links 150, 151 with pairs of shoulder bolts.

The left and right wheel uprights 140, 130 can also include integral(e.g., overmolded) wheel axles, or the wheel axles can be assembled(e.g., pressed) into the left and right wheel uprights 140, 130. Forexample, the left and right wheel axles 143, 133 can include solid,hardened-steel axles and can be pre-machined and press-fit into axlebores in the left and right wheel uprights 140, 130. However, the upperand lower lateral links 150, 151 and the left and right wheel uprights140, 130 can be of any other material and can be manufactured in anyother way.

As described below, when the four-bar linkage is assembled, the left andright wheel axles 143, 133 can extend outwardly from the left and rightwheel uprights 140, 130 with the axes of the left and right wheel axles143, 133 located above a horizontal centerline between the upper andlower lateral links 150, 151 such that: the roll center of the truck 100is below the axes of the wheel assemblies; and such that load on thedeck 212 of the scooter (e.g., the rider) carried into the cam block 110naturally rights the truck 100 (i.e., biases the truck 100 into theneutral position), thereby improving stability of the scooter both whenstopped and when in motion.

For example, the right wheel upright 130 can include: a right upperjunction pivotably coupled to the right end upper lateral link 150; anda right upper junction arranged below the right upper junction andpivotably coupled to the right end of the lower lateral link 151.Similarly, the left wheel upright 140 can include: a left upper junctionpivotably coupled to the left end upper lateral link 150; and a leftlower junction arranged below the left upper junction and pivotablycoupled to the left end of the lower lateral link 151. In this example,the right wheel axle 133 extends outwardly from the right wheel upright130 and is arranged above a horizontal centerline between the rightupper junction and the right lower junction to locate a roll center ofthe upper lateral link 150 and the lower lateral link 151 below theright wheel axle 133. Similarly, the left wheel axle 143 extendsoutwardly from the left wheel upright 140 and is arranged above thehorizontal centerline between the left upper junction and the left lowerjunction to locate the roll center of the upper lateral link 150 and thelower lateral link 151 below the left wheel axle 143.

In one implementation shown in FIG. 4, the upper and lower lateral links150, 151 and the left and right wheel uprights 140, 130 form aparallelogram and thus cooperate to maintain a roll angle between theleft and right wheel axles 143, 133—and therefore the left and rightwheels 144, 134—over a range of deck 212 roll angles. For example, whileno load is applied to the deck 212 or while the weight of the rider islaterally balanced over the deck 212, the upper lateral link 150, thelower lateral link 151, and the left and right wheel uprights 140, 130are biased (e.g., by gravity, the weight of the rider, and/or the springelement 180) into a rectangular arrangement in which the four-barlinkage locates left and right wheel axles 143, 133 coaxially. However,when the rider then shifts her weight laterally over the right side ofthe deck 212, the deck 212 rolls clockwise, thereby shifting the upperlongitudinal axle rightward and the lower longitudinal shaft leftward,rolling the left and right wheel uprights 140, 130 clockwise, incliningthe left and right wheels 144, 134 to the right, increasing contactforce between the outer corner of the right wheel 134 and pavement,increasing contact force between the inner corner of the left wheel 144and pavement, and shifting the effective contact patches of the left andright wheels 144, 134 rightward to balance the rider's shifted weight.

Furthermore, the upper and lower pivot bores in, 112 in the cam block110 can be inclined toward the front of the truck 100 (e.g., by 10°)such that the four-bar linkage locates the wheels with positive caster(e.g., 10°) and induces bump-steer when the four-bar linkage is upsetfrom the rectangular arrangement (e.g., when the rider leans leftward orrightward on the deck 212), thereby enabling the right to steer thescooter by leaning on the deck 212 (or “carving”).

5. Pivot Block and Cam Block

As shown in FIG. 3, the truck 100 includes a cam block 110 and a pivotblock 120 interposed between the cam block 110 and the lower laterallink 151.

The cam block 110 can be cast, molded, forged, and/or machined, etc.(e.g., in steel or aluminum) to include: a mounting flange configured tofasten to a deck 212; an upper pivot bore 111; a lower pivot bore 112;and a counterbore 113 centered about the lower pivot bore 112 and insetfrom the rear of the cam block 110. In one implementation, thecounterbore 113 defines a cylindrical section coaxial with the lowerpivot bore 112 and a set of three hemispherical bores—inset from thebase of the counterbore 113—spaced radially about the lower pivot bore112. A set of three hardened-steel spherical bearings are then installedin these hemispherical bores to form a multi-lobed cam configured tomate with three corresponding lobes in the pivot block 120. For example,these spherical bearings can be bonded and fixed in these bores.Alternatively, these spherical bearings can be sized for a running fit(e.g., 0.0005 undersized radius) within the hemispherical bores and canbe greased before installation in these bores such that these sphericalbearings rotate within their bores when running along followers 122 inthe pivot block 120.

Accordingly, the pivot block 120 can include a cylindrical boss 121extending forward from the lower lateral link 151, undersized for asliding fit within the counterbore 113, and including a coaxial axlebore. The leading face of the cylindrical boss 121 can include a set ofradially-patterned followers 122 configured to mate with the set of camlobes 114 defined by spherical bearings in the base of the counterbore113 of the cam block 110. For example, the pivot block 120 can be cast,forged, molded, sintered, and/or machined in bronze (e.g., for reducedwear of the followers 122 running along the set of cam lobes 114),steel, or aluminum.

5.1 Adjustable Thrust Angle

Additionally or alternatively, the pivot block 120 can include aseparate faceplate—in a hardened material (e.g., steel) and/or low-wearmaterial (e.g., bronze, nylon)—that defines the set ofradially-patterned followers 122 and keys into the leading face of thecylindrical boss 121. In this implementation (and similar to thevariation shown in FIG. 5), the truck 100 can include a set ofreplaceable faceplates defining different follower profiles, such as: ahigh-rake (e.g., a high thrust angle) profile that produces a restoringforce that increases rapidly with greater roll angles; a low-rake (e.g.,a lower thrust angle) profile that produces a restoring force thatincreases less rapidly with greater roll angles; and alternativeprofiles that produce non-linear restoring forces as a function of rollangle. The rider or a technician may therefore replace these faceplateson the pivot block 120 to modify thrust angle between the cams in thecam block 110 of followers 122 in the pivot block 120 and thus modify arelationship between roll angle of the cam block 110 and the restoringforce applied by the truck 100.

In a similar variation, the truck 100 includes a kit of pivot blocks120, wherein each pivot block 120 includes a set of integral followers122 that define a unique profile within the kit. The rider or atechnician may therefore exchange whole pivot blocks 120 in the truck100 with other pivot blocks 120 in the kit to modify thrust anglebetween the cams in the cam block 110 of followers 122 in the pivotblock 120 and thus modify a relationship between roll angle of the camblock 110 and the restoring force applied by the truck 100.

5.2 Lower Longitudinal Shaft

The cam block 110 can also include a spring seat on a front side of thecam block 110 and coaxial with the lower pivot bore 112. A lowerlongitudinal shaft 161—such as in the form of a threaded shoulderbolt—can be inserted: into a longitudinal bore in the center of thelower lateral link 151; through the axle bore of the pivot block 120;through the lower pivot bore 112 of the cam block 110; and past thespring seat. The spring element 180 (e.g., a coil spring) can then beinstalled over the threaded end of the lower longitudinal shaft 161extending fore of the spring seat, and a lower locknut can be threadedonto the threaded end of the lower longitudinal shaft 161 and tightenedagainst the spring element 180, thereby drawing the followers 122 of thepivot block 120 into the cam heels 115 in the cam block 110 andcentering the lower lateral link 151 in a “neutral” position.

5.3 Upper Longitudinal Shaft

Similarly, an upper longitudinal shaft 160—such as in the form of athreaded shoulder bolt—can be inserted: into a longitudinal bore in thecenter of the upper lateral link 150; and through the upper pivot bore111 of the cam block 110. An upper locknut can be threaded onto thethreaded end of the lower longitudinal shaft 161 and tightened againstthe cam block 110 (or a thrust washer), fastening the upper lateral link150 to the cam block 110.

Thus, when the deck 212 rotates about its roll axis, the cam block 110can track with the roll orientation of the deck 212 and rotate relativeto the pivot block 120, which drives the followers 122 of the pivotblock 120 out of the cam heels 115 and up the set of cam lobes 114,thereby: displacing the pivot block 120 rearward; decreasing caster ofthe left and right wheel uprights 140, 130; drawing the lowerlongitudinal shaft 161 rearward; further compressing the spring element180 between the lower locknut and the spring seat; and increasing therestoring force applied by the set of cam lobes 114 on the pivot block120.

5.4 Example

In one example of the foregoing implementations, the cam block 110includes a housing defining: the upper pivot bore 111; the lower pivotbore 112; and a set of hemi-spherical receptacles. In this example, thecam block 110 also includes a set of (e.g., three) spherical bearings:of a first hardness; located in the set of hemi-spherical receptacles;and defining the set of cam lobes 114. In this example, the pivot block120 includes a unitary structure: of a second hardness less than thefirst hardness; and defining the set of followers 122 configured to rideover the set of spherical bearings. In particular, in this example: thehousing can include a cast aluminum structure; the set of sphericalbearings can include hardened steel spherical bearings; and the pivotblock 120 can include a unitary sintered-bronze structure.

In this example, the truck 100 can further include a lower longitudinalshaft 161: arranged in the lower pivot bore 112; and pivotably couplingthe lower lateral link 151 and the pivot block 120 to the cam block 110.The cam block 110 can define: a counterbore 113 arranged about the lowerpivot bore 112; and the set of cam lobes 114 in a base of thecounterbore 113. The pivot block 120 defines: a cylindrical boss 121supported by the counterbore 113 and configured to rotate about andtranslate along an axis through the lower pivot bore 112 responsive to atorque applied to the cam block no; and the set of followers 122 on aface of the cylindrical boss 121.

Furthermore, in this example, the truck 100 can include a seal 123arranged between the boss and the counterbore 113 and configured to seala lubricant packed around the set of cam lobes 114 (e.g., the set ofspherical bearings) and the set of followers 122.

5.5 Variation: Alternate Cam Lobe and Follower Configurations

In one variation, the foregoing cam and follower geometry is invertedsuch that: the pivot block 120 includes the set of cam lobes 114 and camheels 115; and the cam block 110 defines a complementary set ofradially-patterned followers 122. For example, in this variation: thepivot block 120 can include the set of hemispherical bores that locatethe set of spherical bearings to form the set of cam lobes 114; and thecam block 110 can define a complementary set of radially-patternedfollowers 122.

In another variation, the cam block 110 (or the pivot block 120) definesa unitary structure that directly defines the set of cam lobes 114 andthe set of cam heels 115.

5.6 Variation: Reversed Truck

As shown in FIG. 4, with the truck 100 installed on the rear of thescooter, the spring element 180: can be arranged on the leading end ofthe truck 100; and can draw the pivot block 120 forward into the camblock 110. In this configuration, forward motion and/or forwardacceleration of the scooter (such as induced by a wheel upright motor ina puller configuration at the front of the scooter) can induce a loadpath through the scooter than pulls the rear wheel assemblies rearward,thereby reducing the contact force between the set of cams and the setof followers 122, which may reduce the “stiffness” of the truck 100,reduce stability of the rear of the scooter, and enable greater carvingat increasing speeds and/or under greater acceleration. Braking at therear wheel assemblies, such as described below can similarly induce aload path through the scooter than pulls the rear wheel assembliesrearward, thereby reducing the contact force between the set of cams andthe set of followers 122, which may reduce the “stiffness” of the truck100.

Therefore, in one variation, truck 100 is reversed on the rear of thescooter such that acceleration of the scooter (e.g., by the wheelupright motor at the front of the scooter) and braking of the scooter atthe rear wheel assemblies induces a load path through the scooter thatdrives the cam block 110 into the pivot blocks 120, thereby increasingthe contact force between the set of cams and the set of followers 122,which may increase the “stiffness” of the truck 100 and increasestability of the rear of the scooter at increasing speeds, under greateracceleration, and under braking.

5.6 Variation: Constant-Caster

In one variation shown in FIG. 5, the pivot block 120 is pivotablycoupled to the lower pivot bore 112 in the cam block 110 and located ata fixed longitudinal position on the cam block 110 such that the truck100 retains the left and right wheels 144, 134 at a constant casterangle over a range of roll angles.

In one implementation, the cam block 110: defines a splined receptaclecoaxial with the lower pivot bore 112; and includes a multi-lobed camthat runs in and is keyed to the splined receptacle. The multi-lobed camdefines the set of cam lobes 114 and the set of cam heels 115 arrangedradially about the splined receptacle and the lower pivot bore 112. Thepivot block 120 is pivotably coupled to the lower pivot bore 112adjacent the splined receptacle. The spring element 180 biases themulti-lobed cam toward the pivot block 120 to drive the followers 122 ofthe pivot block 120 into the cam heels 115 and therefore bias the lowerlateral link 151 to the neutral position.

For example, the lower longitudinal shaft 161 can run through themulti-lobed cam to pivotably couple the pivot block 120 to the cam block110 and to constrain the longitudinal position of the pivot block120—and therefore the lower lateral link 151—relative to the cam block110. The multi-lobed cam can run in the splined receptacle and slideover the lower longitudinal shaft 161, and the spring element 180 can belocated in a base of the cam block 110 between the cam block 110 and themulti-lobed cam to drive the multi-lobed cam toward the pivot block 120and thus bias the lower lateral link 151 to the neutral position.

Thus, in this variation, the pivot block 120 and the cam block 110 cancooperate to both: compress the spring element 180 when the pivot block120 is rotated off of the neutral position; and maintain thelongitudinal position of the lower lateral link 151 on the pivot block120, thereby maintaining the caster angle of the wheel uprights over therange of deck 212 roll angles.

6. Spring Element

As shown in FIGS. 1A, 2A, 5, and 6, the truck 100 includes a springelement 180 mounted between the deck 212 and the pivot block 120.Generally, the spring element 180 is configured to absorb and counterlongitudinal displacement of the pivot block 120 relative to the camblock 110 as the deck 212 and the cam block 110 roll during operation ofthe scooter.

In particular, rotation of the cam block 110 relative to the pivot block120, the lower lateral link 151, the wheel uprights, etc. duringoperation of the scooter (e.g., when a rider steps onto the scooter ornavigates the scooter around a turn) rotates the cam block 110 relativeto the pivot block 120, drives the set of followers 122 in the pivotblock 120 up the set of cams in the cam block 110, and drives the camblock 110 and the pivot block 120 apart along the axis of the lowerlongitudinal shaft 161. Accordingly, separation of the pivot block 120from the cam block 110 compresses the spring element 180, therebyincreasing the force applied by the spring element 180 against to thepivot block 120 to drive the pivot block 120 and the cam block 110 backtogether. Therefore, the spring element 180 can exert a linear force onthe lower longitudinal shaft 161 to pull followers 122 of the pivotblock 120 into the cam heels 115 of the cam block 110, which translatethis linear force into a torque—or “restoring force”—opposite thedisplacement of the deck 212 from the neutral position, thereby drivingthe truck 100 back to its neutral (or “upright”) position. The springelement 180 can therefore cooperate with the pivot block 120 and the camblock 110 to improve roll stability of the scooter.

In one implementation shown in FIGS. 1A, 2A, 5, and 6, the springelement 180 includes a coil spring interposed between the cam block 110and lower longitudinal shaft 161. However, the spring element 180 caninclude a spring of any other type (e.g., a urethane block, a hydraulicor pneumatic spring) and can be configured to apply an increasingrestorative force to the pivot block 120 and the cam block 110 whencompressed (or tensioned) responsive to rotation of the cam block110—relative to the pivot block 120—away from the neutral position.

6.1 Spring Element Adjustment

In one implementation, the lower longitudinal shaft 161: is arranged inthe lower pivot bore 112; pivotably couples the lower lateral link 151and the pivot block 120 to the cam block 110; and includes a retentionsection 162 extending past the lower pivot bore 112 opposite the pivotblock 120. In this implementation, the truck 100 also includes aretainer 163 arranged on the retention section 162 of the lowerlongitudinal shaft 161 and configured to retain the spring element 180over the lower longitudinal shaft 161. In this implementation, thespring element 180: is arranged between the cam block 110 and theretainer 163; and tensions the lower longitudinal shaft 161 to bias thelower lateral link 151 toward the neutral position, the cam block 110and the pivot block 120 cooperating to locate a top of the deck 212parallel to the lower lateral link 151 in the neutral position.

For example, a threaded end of the lower longitudinal shaft 161 candefine the retention section 162, and the retainer 163 can include athreaded nut. Accordingly, the rider (or a technician) may tighten theretainer 163 on the threaded end of the lower longitudinal shaft 161 toincrease preload on the spring element 180 (e.g., a coil spring), thusincreasing the restoring force applied by the truck 100 to the deck 212over a full range of roll angles of the scooter.

Therefore, in this implementation, the retainer 163 can be adjustable onthe lower longitudinal shaft 161 to modify preload on the spring element180. Accordingly, the spring element 180 can control a) a face pressurebetween the set of cam lobes 114 in the cam block 110 and the set offollowers 122 in the pivot block 120 and b) a minimum torquethreshold—applied to the cam block 110 via the deck 212 of thescooter—to drive the lower lateral link 151 out of the neutral positionthat are proportional to preload on the spring element 180.

6.2 Kit of Spring Elements

In one variation, the truck 100 includes a kit of interchangeable springelements 180 spanning a range of spring constants and/or free lengths.Thus, in this implementation, the rider or a technician may exchangespring elements 180 in the truck 100 in order to modify dynamics (e.g.,stiffness, roll stability) of the scooter.

For example, the rider or the technician may exchange a weaker springelement 180 in the truck 100 for a stiffer spring element 180—such as byremoving the nut described above from the threaded end of the lowerlongitudinal shaft 161 to release the weaker spring element 180,installing the stiffer spring element 180, and reinstalling the nut onthe threaded end of the lower longitudinal shaft 161—in order toincrease the restoring force applied by the truck 100 to the deck 212 ofthe scooter per degree of roll of the deck 212 and thus increasestability of the scooter when stopped and when at speed. Similarly, therider or the technician may exchange a stiffer spring element 180 in thetruck 100 for a weaker spring element 180 in order to decrease therestoring force applied by the truck 100 to the deck 212 of the scooterper degree of roll of the deck 212 and thus enable more rapid carving(or slalom) motions with the scooter.

7. Stability Customization and Controls

In one variation, the truck 100 includes or interfaces with a manual orelectromechanical control module 170 to implement on-the-fly adjustmentof preload of the spring element 180—and therefore implement on-the-flyadjustment of roll stability of the scooter.

7.1 Eccentric Retainer with Preload Range

In one implementation shown in FIG. 6, a thrust washer is arranged onthe lower longitudinal shaft 161 between the spring element 180 and theretainer 163 (e.g., the nut). An eccentric snail (or “drop”) camfollower: is mounted to (or adjacent) the nut at the end of the lowerlongitudinal shaft 161; and defines an eccentric cam face that runs onthe thrust washer opposite the spring element 180. (Alternatively, inthis implementation, the snail cam can be interposed between the springelement 180 and the cam block 110.)

In this implementation, a control lever is mounted: to a handlebar 226of the scooter for manipulation with a rider's hand or thumb duringoperation; or to the deck 212 of the scooter (e.g., near the rear of thedeck 212) for operation by the rider's rear foot while riding thescooter. A pair of push-pull cables (e.g., braided steel cables) arecoupled to the snail cam and to the control lever: such that movement ofthe control lever in a first direction rotates the snail cam in a firstdirection to drive the thrust washer up the eccentric cam face andincrease preload of the spring element 180; and such that movement ofthe control lever in a second direction rotates the snail cam in asecond direction to release the thrust washer down the eccentric camface and decrease preload of the spring element 180.

For example, a novice rider may select and maintain the highest possiblepreload of the spring element 180 in order to maximize the rollstability and rigidity of the scooter. Conversely, an intermediate oradvanced rider may select a lower preload of the spring element 180 inorder to achieve faster, more responsive lean-steer or otherwisedynamically adjust the preload of the spring element 180 based on herspeed, road conditions, etc.

7.2 Bi-Stable Eccentric Retainer

Alternatively, in the foregoing implementation, the control lever and/orthe snail cam can be bi-stable such that actuation of the control levertransitions the snail cam between “high-preload” and “low-preload”positions. For example, the lower nut can be manually tightened by therider—with the control lever in “high-preload” position by default—priorto operation of the scooter in order to set a preferred roll stabilityof the scooter, such as a high preload and high roll stability for easeof onboarding (e.g., for a novice rider) and low-speed operation. Uponreaching moderate speed range during operation, the rider may flip thecontrol lever to the “low-preload” position in order to rapidlytransition the snail cam to the low-preload position, reduce compressionof the spring element 180, and thus reduce roll stability and increaseresponsiveness of the scooter during cornering and carving motions. Uponincreasing or reducing her speed and moving outside of this moderatespeed range, the rider may flip the control lever back to the default“high-preload” position in order to rapidly transition the snail camback to the high-preload position, increase compression of the springelement 180, and thus increase high-speed and low-speed roll stabilityof the scooter.

7.3 Eccentric Retainer with Ratchet Control

Yet alternatively, the truck 100 can include a manually-actuated footpedal or foot switch located on the deck 212, such as near the rear ofthe deck 212 for operation by the rider's back foot while riding thescooter. In this implementation, the foot pedal can be coupled to aratchet, and the ratchet can be coupled to the snail cam directly or viapush-pull cables, etc.

In this implementation, the ratchet can also include a bi-modal ratchetpawl coupled to a second foot switch or controlled directly by motion ofthe foot pedal in a secondary direction. Thus, when the rider actuatesthe foot pedal with the second foot switch—and therefore the bi-modalratchet pawl—in a first position, the foot pedal can drive the ratchetin a first direction, which rotates the snail cam in a first direction,drives the thrust washer up the eccentric cam face, and increasespreload of the spring element 180. However, when the rider actuates thefoot pedal with the second foot switch—and thus the bi-modal ratchetpawl—in the second position, the foot pedal can drive the ratchet in asecond direction, which rotates the snail cam in a second direction,releases the thrust washer down the eccentric cam face, and decreasespreload of the spring element 180.

7.4 Electromechanical Control

In another implementation, the truck 100 includes a motor geared to thesnail cam—such as via a worm drive—and configured to drive the snail cambetween a low-preload position and a high-preload position responsive tocommands from manually-operated switches on the scooter (e.g., mountedto handlebars 226 of the scooter) or from an autonomous stabilitycontrol module 170 within the scooter.

In a similar implementation, the truck 100 includes a motor coupled tothe nut, such as via a gearbox and/or a timing belt. For example, thenut can be threaded onto the threaded section of the lower longitudinalshaft 161, can include outer gear teeth, and can define a sun gear in aplanetary gearbox. The motor can be mounted to the cam block 110, can becoupled to a ring gear of the planetary gearbox, and thus tighten andloosen the nut on the lower longitudinal shaft 161.

The motor can thus rotate the nut directly on the threaded section ofthe lower longitudinal shaft 161 in order to tighten and loosen the nutagainst the spring element 180, such as: responsive to manual input at abutton or other control interface mounted on the handlebars 226 of thescooter; or responsive to a control output of the stability controlmodule 170. For example, in this implementation, the stability controlmodule 170 can: monitor the speed of the scooter based on a wheel speedof the front wheel assembly 202 of the scooter; actuate the motor in afirst direction to tighten the nut against the spring element 180 andincrease preload on the spring element 180 in order to increase rollstability of the scooter at both low and high scooter speeds (e.g.,below 3 miles per hour above 20 miles per hour or a tspeeds predefinedby the rider); and actuate the motor in a second direction to loosen thenut from the spring element 180 and decrease preload on the springelement 180 in order to increase mobility of the scooter at moderatespeeds (e.g., between 3 miles per hour and 20 miles per hour or within aspeed range predefined by the rider).

Therefore, in this implementation, the truck 100 can include: a remotecontroller (e.g., arranged on a handlebar 226 of the scooter); and anelectromechanical actuator 172 configured to rotate the retainer 163(e.g., the nut) on the retention section 162 (e.g., the threaded end) ofthe lower longitudinal shaft 161 to modify preload on the spring element180 responsive to receipt of a command from the remote controller.Accordingly, the truck 100 can include a speed sensor configured todetect a speed of the scooter. The truck 100 can also include (or becoupled to) a controller actuator 172 configured to automatically:retract the retainer 163 on the retention section 162 of the lowerlongitudinal shaft 161 to decrease preload on the spring element 180responsive to the speed of the scooter falling within a moderate speedrange; advance the retainer 163 on the retention section 162 of thelower longitudinal shaft 161 to increase preload on the spring element180 responsive to the speed of the scooter dropping below the moderatespeed range; and advance the retainer 163 on the retention section 162of the lower longitudinal shaft 161 to increase preload on the springelement 180 responsive to the speed of the scooter exceeding themoderate speed range.

7.5 Adjustable Nut with Manual Control

In another implementation, the nut is threaded onto the threaded sectionof the lower longitudinal shaft 161, includes outer gear teeth, anddefines a pinion gear. The truck 100 also includes a cable: defining afirst end coupled to a control knob at a handlebar 226 on the scooter;running in a flexible torque tube from the control knob to the truck100; defining a second end coupled to a worm gear meshed with the nut;and configured to transmit a torque—input by the rider—from the controlknob to the worm gear to rotate the nut and selectively adjust preloadof the spring element 180.

However, the retainer 163 can define or cooperate with any other featureor mechanism in the truck 100 or the scooter 200 to adjust preload ofthe spring element 180 and thus control stability of the scooter 200when stopped and over a range of speeds.

8. Quick-Release Wheel Assembly

In one variation shown in FIG. 7, the left and right wheel uprights 140,130 cooperate to accept and locate quick-release wheel assemblies, suchas to enable a rider or technician to: quickly replace worn wheelassembly components with new components; and quickly exchange differentwheel assembly components, such as wheels of different sizes,hardnesses, colors, or tread patterns, etc.

8.1 Quick-Release Wheel Assembly with Fixed Axle

In one implementation, the right wheel axle 133 defines a hollow axleextending from and mounted to the right wheel upright 130. In thisimplementation, the right wheel assembly 132 includes: a right wheel134; a right tire mounted to the right wheel 134; a skewer 135configured to run through the hollow section of the right wheel axle133; and a quick-release cam lever 136 coupled to the skewer 135 andconfigured to selectively tension the skewer 135 to retain the rightwheel 134 on the right wheel axle 133.

For example, in this implementation, the right wheel axle 133 can berigidly mounted to the right wheel upright 130, and the right wheelassembly 132 can include: an axle nut 137 threaded onto the skewer 135opposite the quick-release cam lever 136; and a thrust washer, thrustbearing, or tapered bearing between the quick-release cam lever 136 andthe outer face of the right wheel 134. Thus, to install the right wheelassembly 132 on the right wheel upright 130, the rider or a technicianmay: remove the axle nut 137 from a first end of the skewer 135; insertthe first end of the skewer 135 into and through the hollow axle; seat aset of bearings within the right wheel 134 over the right hollow axle;reinstall and adjust the axle nut 137 on the first end of the skewer135; and then close the quick-release cam lever 136 to tension theskewer 135 and retain the right wheel 134 on the right hollow axlebetween the thrust washer or thrust bearing and the right wheel upright130. Then, to remove the right wheel assembly 132 from the right wheelupright 130, the rider or a technician may: open the quick-release camlever 136 to release tension on the skewer 135; remove the axle nut 137from the first end of the skewer 135; and withdraw the right wheelassembly 132 out of the right hollow axle.

Alternatively, in this implementation, the quick-release cam lever 136and the axle nut 137 can be reversed such that the quick-release camlever 136 is arranged between the right wheel upright 130 and the pivotblock 120, shielded by the truck 100, and therefore less accessible todamage or inadvertent release than a quick-release cam lever 136arranged on the outside of the right wheel 134.

The left wheel upright 140 and the left wheel assembly 142 can besimilarly configured.

8.2 Quick-Release Wheel Assembly with Removable Axle

In another implementation shown in FIG. 7, the right wheel upright 130defines an axle slot configured to transiently receive a hollow axle. Inthis implementation, the right wheel assembly 132 includes: a righthollow axle configured to transiently install in the axle slot in theright wheel upright 130; a right wheel 134 mounted to the right hollowaxle via a set of bearings; a right tire mounted to the right wheel 134;a skewer 135 configured to run through the right hollow axle; an axlenut 137 arranged on the skewer 135 and configured to seat on an outerthrust surface of the right wheel 134; and a quick-release cam lever 136coupled to the skewer 135 opposite the axle nut 137 and configured toselectively tension the skewer 135 to retain the right wheel 134 on theright wheel axle 133.

Furthermore, the quick-release cam lever 136 can be configured to: seaton an inner face of the right wheel upright 130 opposite the right wheel134; and tension the skewer 135 to retain the right wheel axle 133within the axle slot and to maintain the right wheel axle 133 and theright wheel 134 between the axle nut 137 and the right wheel upright130.

For example, in this implementation, the right wheel 134, the righttire, the skewer 135, quick-release cam lever 136, the quick-release camlever 136, the hollow axle, and the axle nut 137 can cooperate to form aright wheel assembly 132 separable from the right wheel upright 130following release of the quick-release cam lever 136. Thus, to installthe right wheel assembly 132 on the right wheel upright 130, the rideror a technician may: open the quick-release cam lever 136; insert asection of the right hollow axle—extending inwardly from the right wheel134—into the axle slot in the right wheel upright 130; and then closethe quick-release cam lever 136 such that the quick-release cam lever136 extends rearward from the truck 100 and between the right wheelupright 130 and the pivot block 120. Similarly, to remove the rightwheel assembly 132 from the right wheel upright 130, the rider or atechnician may: open the quick-release cam lever 136 (e.g., by rotatingthe quick-release cam lever 136 toward the pivot block 120); and slidethe right hollow axle out of the axle slot in the right wheel upright130.

The left wheel upright 140 and the left wheel assembly 142 can besimilarly configured.

9. Fenders

As described above and shown in FIGS. 1B and 2B, the left and rightwheel uprights 140, 130 can further include fender mounts configured tolocate fenders 190 over the left and right wheels 144, 134, which mayblock road spray (e.g., water, mud, road debris) moving off of thewheels from reaching the rider. Because these fenders 190 are mounted tothe wheel uprights (e.g., rather than to the deck 212 of the scooter),these fenders 190 may: define small structures located in (very) closeproximity to adjacent wheels without sacrificing effective road sprayblocking or rubbing against these wheels; track with these wheels as thewheels and wheel uprights lean during turns; and remain unobtrusive tooperation of the scooter.

8.1 Folding Hard Fenders+Folder Scooter

In this variation, a fender 190 can include both: a fixed fender 190section (e.g., a trailing section) configured to rigidly mount to awheel upright; and an operable fender 190 section (e.g., a leadingsection). The operable fender 190 section: can be sprung off of theadjacent wheel upright and/or off of the adjacent fixed fender 190section; and can include a braking surface 192 configured to contact andbrake an adjacent wheel, such as when manually depressed by a rider'sfoot.

In one implementation shown in FIGS. 12A, 12B, and 12C, the deck 212defines a “split deck 212” that folds (or “collapses”) about a deckhinge 214 to transition from a “go mode” into a “tow” or “stow” mode, asdescribed in U.S. patent application Ser. No. 16/535,004. In thisimplementation, the deck 212 includes: a front deck section 210; a reardeck section 213 supporting the rear truck 100 opposite the front decksection 210; a deck hinge 214 interposed between the front deck section210 and the rear deck section 213, operable in an open deck positionthat locates the front deck section 210 tangent to the rear deck section213 to form a substantially continuous deck surface, and operable in aclosed deck position to separate the front deck section 210 from therear deck section 213 and raise the deck hinge 214 above the rear truck100; and a deck latch configured to selectively lock the deck hinge 214in the closed deck position. Between operations, the rider may releasethe deck hinge 214 in order to collapse the front and rear deck sections210, 213, thereby transitioning the scooter from the “go” mode into the“tow” mode (e.g., for one-handed lugging analogous to wheeled luggage)or into the “stow” mode (e.g., for storage under a desk or in a luggagecompartment), as shown in FIG. 13.

Thus, to avoid collision with ground discontinuities and to enable therear wheel assemblies on the truck 100 to traverse pavement unobstructedin the “go” mode, these fenders 190 may span a radial section of thewheel excluding a radial section from a 120° position to a 240° positionabout the wheel, as shown in FIGS. 12B and 14. To avoid collision withthe ground and to enable the scooter to remain upright on three wheelsin the “tow” mode, these fenders 190 may also span a radial section ofthe wheel excluding a radial section from a 60° position to a 110°position about the wheel. Furthermore, to avoid collision with grounddiscontinuities and to enable the rear wheel assemblies on the truck 100to traverse pavement unobstructed in the “tow” mode with the scootertugged behind the rider, these fenders 190 may span a radial section ofthe wheel excluding a radial section from a −20° position to a 110°position about the wheel.

Therefore, in this variation, a front fender section 191 of a fender 190can span a radial section from a 240° position to a 310° position aboutthe adjacent wheel when mounted to a fender mount extending from a wheelupright, as shown in FIG. 14. The rear fender section 193 can bepivotably coupled to the fender mount after of the front fender section191 and can span a radial section from the 310° position to the 120°position about the wheel in a “go” position. The front fender section191 can also be spring-loaded on the fender mount such that the frontfender section 191: pivots downward on the fender mount to brake againstthe adjacent wheel when depressed by the rider; and returns to the “go”position when released by the rider.

However, the rear fender section 193 can also pivot forwardapproximately 180° on the fender mount in a “retracted” position toeliminate obstruction of the adjacent wheel from the 310° position tothe 240° position of the wheel in the “tow” and “stow” modes. Forexample, the fender 190 can include a bistable spring that locates therear fender section 193 in either the “go” position or the “retracted”position. In this example, when the scooter is transitioned from the“go” mode to the “tow” or “stow” mode, the rear truck 100 pitchesrearward, causing the rear fender sections 193 on the left and rightfenders 190 to contact the adjacent ground surface and to tension theircorresponding springs. At a threshold position of the rear deck section213 between the “go” mode and the “tow” or “stow” mode, the springsinvert and thus retract the rear fender sections 193 into their“retracted” positions. Conversely, when the scooter is transitioned fromthe “tow” or “stow” mode back into the “go” mode, the rider can tap therear fender sections 193 rearward with her hand or foot to return therear fender sections 193 to their “go” positions.

In a similar implementation, a wheel upright includes a fender mountextending upwardly from its wheel axle. In this implementation, a fender190 includes: a leading brake-fender 190 section pivotably coupled to afender mount; a brake pad mounted (e.g., fastened, bonded) to theunderside of the leading brake-fender 190 section; a brake springinterposed between the leading brake-fender 190 section and the fendermount and configured to lift the leading brake-fender 190 section off ofthe adjacent tire; and a rear fender section 193 mounted to the fendermount. In this implementation, the rear fender section 193 can bepivotably coupled to the fender mount and can be operable between a downposition (e.g., in the “go” mode) and a retracted position (e.g., in the“tow” and “stow” modes). For example, the leading brake-fender 190section and the rear fender section 193 can be pivotably coupled to thefender mount via a common pivot bolt, and a second bistable spring canselectively retain the rear fender section 193 in the down and retractedpositions.

8.1.1 Example

For example, in this implementation, the right wheel upright 130 candefine a right fender mount 131 extending above the right wheel axle133. The truck 100 can include: a right front fender section 191pivotably coupled to the mount, extending forward from the mount, anddefining a braking surface 192 configured to selectively engage andbrake a surface of the right wheel assembly 132, as shown in FIG. 8; anda right rear fender section 193 coupled to mount and extending rearwardfrom the mount. The scooter can include: a front deck section 210defining a front deck surface; a rear deck section 213 defining a reardeck surface, cooperating with the front deck section 210 to define thedeck 212, and supported by the right wheel assembly 132 and the leftwheel assembly 142 via the cam block 110; a deck hinge 214 interposedbetween the front deck section 210 and the rear deck section 213; afront wheel assembly 202 supported on the front deck section 210; and adeck control 215 configured to release the deck hinge 214 for transitionof the deck 212 between an open deck position and a closed deckposition.

For example and as shown in FIGS. 12A and 13, the deck hinge 214 canoccupy the open deck position in a “go” mode of the scooter, wherein thescooter is configured for riding on the first wheel assembly, the rightwheel assembly 132, and the left wheel assembly 142 by a rider in the“go” mode. In this example, the right rear fender section 193 can occupya lowered position in the go mode of the scooter to shield the riderfrom road spray from the right wheel assembly 132. Conversely as shownin FIGS. 12B and 13, the deck hinge 214 can occupy the closed deckposition in a tow mode of the scooter, wherein the scooter is configuredfor manual towing on the right wheel assembly 132 and the left wheelassembly 142 in the tow mode. Furthermore, the right rear fender section193 can occupy a retracted position in the tow mode of the scooter toavoid contact with a ground surface during towing of the scooter on theright wheel assembly 132 and the left wheel assembly 142. In particular,the right rear fender section 193 can be manually rotated from thelowered position to the retracted position (e.g., pivoted about theright fender mount 131 away from the right wheel 134) when the scooteris transitioned from the go mode into the tow mode.

Furthermore, in this example, the scooter can include: a neck hinge 220coupled to the front deck section 210 opposite the deck hinge 214; aneck 222 coupled to the neck hinge 220 opposite the front deck section210; a stem 224 rotatably coupled to the neck 222 and supported by thefront wheel assembly 202; a set of handlebars 226 coupled the stem 224opposite the front wheel assembly 202; and a neck control 228 configuredto release the neck hinge 220 for transition between an open neck 222position and a closed neck 222 position. Accordingly, the neck hinge 220can occupy the open neck 222 position in the go mode of the scooter toenable the scooter to be ridden and steering by the rider; and the heneck hinge 220 can occupy the closed neck 222 position in the tow modefor manual towing by the rider.

The left wheel upright 140 can similarly include a left fender mount 141configured to locate a fender 190 over the left wheel assembly 142.

8.2 Soft Fenders

In another implementation, the fender 190 includes a soft polymerhalf-“cupped” structure: configured to mount to a wheel upright (e.g.,near a 270° position on the adjacent wheel); operable in a concaveposition to cover a radial segment of the adjacent wheel (e.g., from a120° position to a 240° position about the wheel); and operable in aconvex position in which the fender 190 is folded inside-out to render alarge radial portion of the adjacent wheel unobstructed (e.g., from the240° position to a 330° position about the wheel). For example, in thisimplementation, a fender 190 can include an elastic silicone “cup”structure configured to invert between the concave and convex positionto cover and uncover the adjacent wheel.

8.2.1 Soft Fenders

For example, in this implementation, the right fender 190: can includean elastic material (e.g., silicone); can approximate a hemi-ellipsoidalgeometry; can be mounted to the right wheel upright 130 via the rightfender mount 131; and can be operable (e.g., bistable) in a firstconfiguration and an inverted configuration. In particular, the rightfender 190: can extend over a portion of the right wheel assembly 132 inthe first configuration; and can be manually turned inside out toretract over the right wheel assembly 132 in the inverted configuration.

In this example and as described above, the scooter can include: a frontdeck section 210 defining a front deck surface; a rear deck section 213defining a rear deck surface, cooperating with the front deck section210 to define the deck 212, and supported by the right wheel assembly132 and the left wheel assembly 142 via the cam block 110; a deck hinge214 interposed between the front deck section 210 and the rear decksection 213; a front wheel assembly 202 supported on the front decksection 210; and a deck control 215 configured to release the deck hinge214 for transition of the deck 212 between an open deck position and aclosed deck position. Thus, in this example, the deck hinge 214 canoccupy the open deck position in a go mode of the personal mobilityvehicle 200, wherein the personal mobility vehicle 200 is configured forriding on the first wheel assembly, the right wheel assembly 132, andthe left wheel assembly 142 by a rider in the first mode. Furthermore,the right fender 190 can occupy the first configuration in the firstmode of the personal mobility vehicle 200 to shield the rider from roadspray from the right wheel assembly 132. Conversely, the deck hinge 214can occupy the closed deck position in a tow mode of the personalmobility vehicle 200, wherein the personal mobility vehicle 200 isconfigured for manual towing on the right wheel assembly 132 and theleft wheel assembly 142 in the second mode. Furthermore, the rightfender 190 can occupy the inverted configuration in the tow mode of thepersonal mobility vehicle 200 to avoid contact with a ground surfaceduring towing of the personal mobility vehicle 200 on the right wheelassembly 132 and the left wheel assembly 142.

8.3 Extensible Fenders

In another implementation shown in FIGS. 8 and 9, the fender 190includes: a front fender section 191 pivotably coupled to a front of anadjacent wheel upright and defining a braking surface 192; and a rearfender section 193 that slides (or “telescopes”) into and out of thefront fender section 191. In this implementation, the rear fendersection 193: can be extended rearward out of the front fender section191 to cover the rear of the adjacent wheel in the “go” mode; and can beretracted forward into the front fender section 191 to increaseclearance around the adjacent wheel in the “tow” and “stow” modes.

8.4 Rotating Fenders

In a similar implementation shown in FIG. 10, the fender 190 includes: afront fender section 191 pivotably coupled to a front of an adjacentwheel upright and defining a braking surface 192; and a rear fendersection 193 coupled to the front fender section 191 about avertically-oriented pivot. In this implementation, the rear fendersection 193: can be rotated rearward from the front fender section 191to cover the rear of the adjacent wheel in the “go” mode; and can berotated forward to increase clearance around the adjacent wheel in the“tow” and “stow” modes.

8.5 Quick-Change Fender

In the foregoing implementations, the fender 190 can be configured toclamp onto a pivot extending from the adjacent wheel upright, as shownin FIG. 11. In this variation, the truck 100 can also include a kit offenders 190 of different lengths, and these fenders 190 can beselectively installed and removed from the truck 100 by a rider as therider transitions the scooter between modes.

As a person skilled in the art will recognize from the previous detaileddescription and from the figures and claims, modifications and changescan be made to the embodiments of the invention without departing fromthe scope of this invention as defined in the following claims.

I claim:
 1. A system comprising: a cam block configured to mount to adeck of a personal mobility vehicle and defining: an upper pivot bore; alower pivot bore located below the upper pivot bore; and a set of camlobes arranged about the lower pivot bore; a pivot block: coupled to andpivoting about the lower pivot bore; and defining a set of followersconfigured to ride over the set of cam lobes; a right wheel upright; aright axle extending outwardly from the right wheel upright andconfigured to locate a right wheel assembly; a left wheel upright; aleft axle extending outwardly from the left wheel upright and configuredto locate a left wheel assembly; an upper lateral link: coupled to theright wheel upright and the left wheel upright; and coupled to andpivoting about the upper pivot bore; a lower lateral link coupled to:the right wheel upright; the left wheel upright below the upper laterallink; and the pivot block between the right wheel upright and the leftwheel upright; and a spring element coupled to the pivot block andconfigured to drive the set of followers of the pivot block against theset of cam lobes of the cam block to bias the lower lateral link towarda neutral position.
 2. The system of claim 1: wherein the set of camlobes of the cam block defines a set of peaks and a set of valleysinterposed between the set of peaks and arranged about the lower pivotbore; and wherein the spring element is configured to: compress the setof followers of the pivot block to ride up the set of cam lobes of thecam block toward the set of peaks and to enable the lower lateral linkto pivot within the lower pivot bore responsive to application of atorque on the cam block; and drive the set of followers of the pivotblock into the set of valleys of the cam block to return the lowerlateral link toward the neutral position responsive to release of thetorque from the cam block, the cam block and the pivot block cooperatingto locate a top of the deck parallel to the lower lateral link in theneutral position.
 3. The system of claim 1: wherein the cam blockcomprises: a housing defining: the upper pivot bore; the lower pivotbore; and a set of hemi-spherical receptacles; a set of sphericalbearings of a first hardness, located in the set of hemi-sphericalreceptacles, and defining the set of cam lobes; wherein the pivot blockcomprises a unitary structure: of a second hardness less than the firsthardness; and defining the set of followers configured to ride over theset of spherical bearings.
 4. The system of claim 3: wherein the housingof the cam block comprises a cast aluminum structure; wherein the set ofspherical bearings comprise hardened steel spherical bearings; andwherein the pivot block comprises a unitary sintered-bronze structure.5. The system of claim 1: further comprising: a lower longitudinalshaft: arranged in the lower pivot bore; pivotably coupling the lowerlateral link and the pivot block to the cam block; and comprising aretention section extending past the lower pivot bore opposite the pivotblock; and a retainer arranged on the retention section of the lowerlongitudinal shaft; and wherein the spring element: is arranged betweenthe cam block and the retainer; and tensions the lower longitudinalshaft to bias the lower lateral link toward the neutral position, thecam block and the pivot block cooperating to locate a top of the deckparallel to the lower lateral link in the neutral position.
 6. Thesystem of claim 5: wherein the retainer is adjustable on the lowerlongitudinal shaft to modify preload on the spring element; and whereinthe spring element is configured to control a face pressure between theset of cam lobes and the set of followers and a minimum torquethreshold, applied to the cam block via the deck of the personalmobility vehicle, to drive the lower lateral link out of the neutralposition that are proportional to preload on the spring element.
 7. Thesystem of claim 6: wherein the retainer is threaded onto the retentionsection of the lower longitudinal shaft; and further comprising: acontrol module; and an actuator configured to rotate the retainer on theretention section of the lower longitudinal shaft to modify preload onthe spring element responsive to an input at the control module.
 8. Thesystem of claim 6, further comprising: a speed sensor configured todetect a speed of the personal mobility vehicle; and a control moduleconfigured to automatically: retract the retainer on the retentionsection of the lower longitudinal shaft to decrease preload on thespring element responsive to the speed of the personal mobility vehiclereceipt falling within a moderate speed range; advance the retainer onthe retention section of the lower longitudinal shaft to increasepreload on the spring element responsive to the speed of the personalmobility vehicle dropping below the moderate speed range; and advancethe retainer on the retention section of the lower longitudinal shaft toincrease preload on the spring element responsive to the speed of thepersonal mobility vehicle exceeding the moderate speed range.
 9. Thesystem of claim 1: further comprising a lower longitudinal shaft:arranged in the lower pivot bore; and pivotably coupling the lowerlateral link and the pivot block to the cam block; wherein the cam blockdefines: a counterbore arranged about the lower pivot bore; and the setof cam lobes in a base of the counterbore; and wherein the pivot blockdefines: a cylindrical boss: supported by the counterbore; andconfigured to rotate about and translate along an axis through the lowerpivot bore responsive to a torque applied to the cam block; and the setof followers on a face of the cylindrical boss.
 10. The system of claim9, further comprising a seal arranged between the boss and thecounterbore and configured to seal a lubricant packed around the set ofcam lobes and the set of followers.
 11. The system of claim 1: whereinthe right wheel upright defines a right fender mount; and furthercomprising a right fender: comprising an elastic material; mounted tothe right fender mount; and operable in a first configuration and aninverted configuration, the right fender extending over a portion of theright wheel assembly in the first configuration, the right fendersection turned inside out to retract over the right wheel assembly inthe inverted configuration.
 12. The system of claim 11: furthercomprising the personal mobility vehicle comprising: a front decksection defining a front deck surface; a rear deck section defining arear deck surface, cooperating with the front deck section to define thedeck, and supported by the right wheel assembly and the left wheelassembly via the cam block; a deck hinge interposed between the frontdeck section and the rear deck section; a front wheel assembly supportedon the front deck section; and a deck control configured to release thedeck hinge for transition of the deck between an open deck position anda closed deck position; wherein the deck hinge occupies the open deckposition in a first mode of the personal mobility vehicle, the personalmobility vehicle configured for riding on the first wheel assembly, theright wheel assembly, and the left wheel assembly by a user in the firstmode; wherein the right fender occupies the first configuration in thefirst mode of the personal mobility vehicle to shield the user from roadspray from the right wheel assembly; wherein the deck hinge occupies theclosed deck position in a second mode of the personal mobility vehicle,the personal mobility vehicle configured for manual towing on the rightwheel assembly and the left wheel assembly in the second mode; andwherein the right fender occupies the inverted configuration in thesecond mode of the personal mobility vehicle to avoid contact with aground surface during towing of the personal mobility vehicle on theright wheel assembly and the left wheel assembly.
 13. The system ofclaim 1: wherein the right wheel upright defines a right fender mountextending above the right axle; and further comprising: a right frontfender section: pivotably coupled to the mount; extending forward fromthe mount; and defining a braking surface configured to selectivelyengage and brake a surface of the right wheel assembly; and a right rearfender section: coupled to mount; and extending rearward from the mount.14. The system of claim 13: further comprising the personal mobilityvehicle comprising: a front deck section defining a front deck surface;a rear deck section defining a rear deck surface, cooperating with thefront deck section to define the deck, and supported by the right wheelassembly and the left wheel assembly via the cam block; a deck hingeinterposed between the front deck section and the rear deck section; afront wheel assembly supported on the front deck section; and a deckcontrol configured to release the deck hinge for transition of the deckbetween an open deck position and a closed deck position; wherein thedeck hinge occupies the open deck position in a first mode of thepersonal mobility vehicle, the personal mobility vehicle configured forriding on the first wheel assembly, the right wheel assembly, and theleft wheel assembly by a user in the first mode; wherein the right rearfender section occupies a lowered position in the first mode of thepersonal mobility vehicle to shield the user from road spray from theright wheel assembly; wherein the deck hinge occupies the closed deckposition in a second mode of the personal mobility vehicle, the personalmobility vehicle configured for manual towing on the right wheelassembly and the left wheel assembly in the second mode; and wherein theright rear fender section occupies a retracted position in the secondmode of the personal mobility vehicle to avoid contact with a groundsurface during towing of the personal mobility vehicle on the rightwheel assembly and the left wheel assembly, the right rear fendersection pivoted about the mount away from the right wheel in theretracted position.
 15. The system of claim 14: wherein the personalmobility vehicle defines a scooter and further comprises: a neck hingecoupled to the front deck section opposite the deck hinge; a neckcoupled to the neck hinge opposite the front deck section; a stemrotatably coupled to the neck and supported by the front wheel assembly;a set of handlebars coupled the stem opposite the front wheel assembly;and a neck control configured to release the neck hinge for transitionbetween an open neck position and a closed neck position; wherein theneck hinge occupies the open neck position in the first mode of thepersonal mobility vehicle; and wherein the neck hinge occupies theclosed neck position in the second mode of the personal mobility vehiclefor manual towing by the user.
 16. The system of claim 1: wherein theright axle defines a hollow axle extending from and mounted to the rightwheel upright; and further comprising the right wheel assemblycomprising: a right wheel; a right tire mounted to the right wheel; askewer configured to run through the hollow section of the right axle;and a quick-release cam lever coupled to the skewer and configured toselectively tension the skewer to retain the right wheel on the rightaxle.
 17. The system of claim 16: wherein the right wheel uprightdefines a slot configured to transiently receive the right axle; whereinthe right axle assembly further comprises an axle nut arranged on theskewer opposite the quick-release cam lever and configured to seat on anouter thrust surface of the right wheel; wherein the quick-release camlever is configured to: seat on an inner face of the right wheel uprightopposite the right wheel; and tension the skewer to retain the rightaxle within the slot and to maintain the right axle and the right wheelbetween the axle nut and the right wheel upright; and wherein the rightwheel, the right tire, the skewer, quick-release cam lever, thequick-release cam lever, the hollow axle, and the axle nut cooperate toform the wheel assembly separable from the right wheel upright followingrelease of the quick-release cam lever.
 18. The system of claim 1:wherein the right wheel upright comprises: an upper junction pivotablycoupled to the upper lateral link; and a lower junction arranged belowthe upper junction and pivotably coupled to the lower lateral link; andwherein the right axle extends outwardly from the right wheel uprightand is arranged above a horizontal centerline between the upper junctionand the lower junction to locate a roll center of the upper lateral linkand the lower lateral link below the right axle.
 19. A systemcomprising: a cam block configured to mount to a deck of a scooter anddefining: a first pivot feature; a second pivot feature verticallyoffset from the first pivot feature; a set of cam lobes arranged aboutthe second pivot feature; and a set of cam heels between the set of camlobes; a pivot block: coupled to and pivoting about the second pivotfeature; and defining a set of followers configured to ride over the setof cam lobes; a pair of wheel uprights configured to locate a pair ofwheel assemblies; a first lateral link: extending between and coupled tothe pair of wheel uprights; and coupled to and pivoting about the firstpivot feature; a second lateral link: extending between and coupled tothe pair of wheel uprights; vertically offset from the first laterallink; and coupled to the pivot block between pair of wheel uprights; anda spring element coupled to the pivot block and configured to drive theset of followers of the pivot block into the set of cam heels to biasthe second lateral link toward a neutral position.
 20. A personalmobility vehicle comprising: a deck configured to support a user; a camblock mounted to the deck and defining: a first pivot feature; a secondpivot feature vertically offset from the first pivot feature; and afirst set of lobes arranged about the second pivot feature; a pivotblock: coupled to and pivoting about the lower pivot feature; anddefining a second set of lobes configured to ride over the first set oflobes; a right wheel upright; a left wheel upright; a right wheelassembly mounted to the right wheel upright; a left wheel assemblymounted to the left wheel upright; a first lateral link pivotablycoupled to the first pivot feature; a second lateral link coupled to thepivot block and cooperating with the right wheel upright, the left wheelupright, and the first lateral link to form a four-bar linkage thatlocates the right wheel assembly and the left wheel assembly on the camblock; and a spring element coupled to the pivot block and configured todrive the second set of lobes the pivot block against the first set oflobes of the cam block to bias the lower lateral link toward a neutralposition, the cam block and the pivot block cooperating to locate a topof the deck parallel to the second lateral link in the neutral position.